An accessory gear box (AGB) is mounted on a gas turbine engine and drives various support components required to sustain engine operation. The support components include but are not limited to a fuel pump, an oil pump, an air driven starter, and air/oil separator, and an electrical generator. These components, the gearbox and the engine itself must fit within a confined space called an engine nacelle.
Referring to FIG. 1, a typical gas turbine engine 100 comprises of a compressor section 5, a combustion section 10 and a turbine section 15 arranged sequentially in that order. All of these sections are roughly cylindrical and oriented coaxially. A set of compressor blades in the compressor section 5 and a set of turbine blades in the turbine section 15 are driven in tandem by the engine drive shaft 30 extending coaxially completely through the gas turbine engine 100 from the compressor section 5 to the turbine section 15.
A tower shaft that is driven by bevel gears off of the drive shaft is typically used to transfer power from the drive shaft 30 to the auxiliary gearbox that is located outside of the exterior casing of the gas turbine engine and inside the nacelle or engine bay. A conventional gear box has at least one gear axis 41 running parallel with the engine drive shaft 30. The AGB 40 drives the support components 42 via a series of interlocking drive gears (See, FIG. 1B) that are oriented orthogonally to the gear axis 41. Each of the support components 42 are arranged arcuately around the engine casing 50 and located radially away from the drive shaft 30 and are situated outboard of the widest cylindrical section of the gas turbine engine (e.g., the air collector 45) in order to fit within the nacelle or the engine bay and also not interfere with the engine casing 50. This positioning is necessary because the irregular radius of the gas turbine engine casing 50 physically precludes the combined auxiliary gear box 40 and its support components 42 from being installed any closer to the drive shaft of the gas turbine engine.
The relatively long tower shaft 35 driving the AGB 40 and the disbursed, arcuate arrangement of the support components 42 (see, FIG. 1B) produces a significant churning of lubrication oil within the AGB 40 and results in less than efficient lubrication and lubrication oil scavenging. The arrangement also requires an unnecessarily large amount of space within the nacelle or engine bay (See, FIG. 3).
Accordingly, it is desirable to provide an alternative gearbox architecture that allows the gearbox to be compactly contoured and positioned closer to the exterior engine casing to reduce weight and improve oil scavenging.
In addition, it is desirable to provide a gearbox architecture providing superior oil scavenging from the gearbox housing. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.